1. Field of the Invention
The present invention relates to a steam reforming catalyst for hydrocarbons for production of hydrogen, synthetic gases or town gases, and a method of producing the catalyst.
2. Related Art Statement
Heretofore, catalysts having catalytically active component Ni or Co supported on alumina-based carriers have been widely used as catalysts for reforming hydrocarbons. Platinum group noble metals, such as Rh and Ru, can be used also as the active components. However, they are so expensive that they have not been used so widely as Ni and Co, though they have higher activities than Ni and Co.
Carriers made of oxide of Mg, Ca, Sr, Ba, Al, Ce, Si, Ti, Zr, or combinations of at least two thereof are known. Among them, alumina is mostly used as the carrier from the viewpoints of mechanical strength, heat resistant property and chemical stability, etc. An improved alumina carrier added with an oxide of an alkaline earth metal is also known. For example Japanese Patent Application Publication No. 44-17,737 discloses a reforming catalyst added with 10-20 wt % of Mg, Ca, Sr or Ba, which has less deposition of carbon thereon during the use in the reforming reaction.
Further, Japanese Patent Application No. 61-264,097 (Laid-open No. 63-141,643) discloses a catalyst prepared by supporting at least one of V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Ag, Cd, La, Ce, perovskite and platinum group noble metals on a carrier containing aluminum oxide and a metal oxide expressed by MeO (Me is Ca, Ba or Sr) in a mol ratio of 100:(3-25), which is mainly used for catalytic combustion processes.
Catalysts using conventional alumina series carriers have the following drawbacks;
(1) If Ni or Co supported on alumina is exposed to a high temperature oxidizing atmosphere, nickel aluminate or cobalt aluminate which is a compound of Ni or Co and alumina is formed to decrease the catalyst activity.
(2) During the reforming reaction, the surface of the catalyst is covered by carbon formed by reactions, such as disproportionation of CO and decomposition of CH.sub.4, to decrease the strength and the activity of the catalyst.
For obviating the drawback (2), an attempt has been made to add a basic component to the alumina to neutralize the acid point of the alumina. However, if K is added as the basic component to the alumina, K is dissipated from the catalyst during the reforming reaction. While, if MgO is added as the basic component to the alumina, hydroxide of Mg is formed in the presence of steam, so that the formed catalyst assumes a powdery state during the reforming reaction.